1. Field of the Invention:
The invention relates to a valving system for effecting the inflation of an inflatable packer.
2. Summary of the Prior Art:
As schematically shown in FIGS. 1 and 2 of the drawings, the prior art has heretofore provided a three valve system for effecting inflation of an inflatable packer. The three valves are respectively well known as a locking shut-off valve, a poppet valve and an inflate limit valve which are connected in series to transmit a fluid pressure from the interior of a hollow mandrel to the interior of an annular inflatable packing element which surrounds the mandrel. The three valves are disposed in a tubular valve collar within which the valves are mounted in chordal relationship. The tubular valve collar surrounds the mandrel and is sealingly secured to one end of the annular inflatable element.
The locking shut-off valve prevents any fluid flow into the valving system until the fluid pressure within the mandrel bore exceeds the well bore pressure by a preselected amount. Once such pressure is supplied, the locking shut-off valve moves to a fully open position permitting fluid to flow to the poppet valve which in turn opens at a low pressure to supply pressure to the inflate limit valve. The inflate limit valve transmits the pressure supplied from the poppet valve to the interior of the inflatable element of the inflatable packer. A return conduit from the inflate chamber of the inflatable packing element applies a counteracting pressure to the valve element of the inflate limit valve to cut off further fluid flow from the poppet valve when the inflatable element is fully inflated A subsequent reduction in fluid pressure within the bore of the hollow mandrel permits the locking shut-off valve to return to a closed, locked position relative to the conduit connecting such valve element with the mandrel bore and the poppet valve also assumes a closed position under a spring and inflatable element pressure bias.
This system has functioned well when the inflatable packer is inflated by hydrocarbon fluids commonly employed in wells. In some applications, it is desirable to inflate the packer with cementing fluid and thus achieve the permanent inflation of the packer with a solid filling of cement. The greater viscosity and solids content of the cementing fluid results in substantial flow damage to the poppet valve and inflate limit valve. Since these valves are mounted in chordal relationship in the tubular wall of the valve collar, it is not possible to increase the flow area through these last mentioned valves by merely increasing the dimensions of such valves because they already occupy all of the space permitted by the relatively small wall thickness of the tubular valve collar.
There is, therefore, a definitive need for modifying a conventional three valve system to increase flow areas through the poppet and inflate limit valves to reduce flow velocity and damage caused by high velocity flow.